A low-cost high-precision constant-temperature mini chamber based on the natural convection principle is presented in this paper. The chamber is assembled using hollow acrylic walls whose sizes are tailored according to the required space. A thin layer of vacuum insulation plate (VIP) with an ultralow thermal conductivity coefficient is adhered around the inner walls so as to prevent heat exchange with room air. A high-precision temperature sensor measuring the temperature near the instrument's measuring point provides a feedback signal to a proportional integral derivative (PID) controller. Thermoelectric coolers uniformly arranged on the ceiling of the chamber are used to cool the air inside the chamber directly without any air supply system, yielding a vibration-free cooling system. A programmable power supply is used as the driver for the coolers to generate different cooling capacities. In practice, the down-flowing cool air and the up-flowing hot air form a natural convection, and the air temperature in the chamber gradually becomes stable and finally reaches the temperature set by the PID controller. Experimental results show that the system's steady-state error is 0.0043 ℃ on average, and the variation range is less than ±0.02 ℃ when the set temperature is 20 ℃, which is much better than the requirement of a Class I standard room. This innovative low-cost, vibration-free, and low-energy-consumption temperature-controlled chamber can be used in micro/nanomeasurement or manufacturing applications and its volume can be custom-designed for any equipment.